Happened to me this morning, on only my 3rd ride on my new Cannondale Quick Speed 1. Had a total blowout in the rear, I think I might have overinflated the tire before I left for the ride. A 30 mile ride turned into a 7 mile ride and a 5 mile walk with the bike, back to my car. That was not fun as I do not enjoy walking in the least! Next time, I am parking my car dead center of my route so that I minimize the walk just in case it ever happens again.